1. Field of the Invention
The invention relates to a tilt and swivel positioning device for positioning a servo flap in a rotor blade. The device contains a tilt element and a bearing element in which the tilt element swivels about the bearing element.
2. The Prior Art
Tilt and swivel positioning devices are used for spatial positioning of components relative to other components by tilting or swivelling movements about a swivel axis. Usually, the component is connected to the other components via a tilt or swivel joint. Furthermore, drive means or retention means are required to set the respective desired position of the component in relation to the other component.
Known tilt and swivel positioning devices include prestressed crank mechanisms having slide bearings or roller bearings. However, the crank-mechanisms are associated with relatively high friction losses. In addition, a change in friction forces in the dead center of movement occurs, (the so-called stick slip) making exact control of the movement sequence difficult. For some applications, roller bearings are too large or their capacity to withstand mechanical load is insufficient.
These disadvantages are significant when using tilt and swivel positioning devices for positioning a servo flap in a rotor blade of a helicopter. The servo flaps make it possible to vary the shape of a rotor blade to reduce aircraft noise and vibrations. Furthermore, the aerodynamics of the rotor blade can be improved. These servo flaps and bearings are also be subjected to considerable mechanical loads. In addition, the available design space is relatively small.
Tilt and swivel positioning devices for positioning a servo flap in a rotor blade of a helicopter are described in U.S. Pat. Nos. 5,639,215, 5,387,083 and 5,409,183. These tilt and swivel positioning devices contain the above-mentioned disadvantages.
Therefore, it is an object of the present invention to provide an improved tilt and swivel positioning means.
This and other objects are accomplished by providing a tilt and swivel positioning device for positioning a servo flap in a rotor blade. The device contains a tilt element and a bearing element. The tilt element swivels about the bearing element. The bearing element comprises a convex roll-off surface held against a concave roll-off surface. The radius of the concave roll-off surface exceeds the radius of the convex roll-off surface.
Instead of crank bearings or roller bearings, there is the interaction of two roll-off surfaces. In this way, transmission of considerable forces and a highly rigid construction, even in a confined design space, is provided. The present invention also allows essentially play-free conversion of linear movement to tilting or rotational movement with little friction loss. The use of the present device for positioning the servo flap provides fast control of the aerodynamics for each individual blade, with tracking, vibration reduction, noise reduction and stall control. Overall, the aerodynamic performance is improved.